JP2706787B2 - Variable steering gear ratio device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable steering gear ratio device that varies a vehicle steering angle with respect to a steering wheel steering angle of a vehicle.

(Prior Art) In four-wheel steering, it has been found that controlling the steering angles of the front wheels and the rear wheels enhances the motion characteristics during turning.

That is, at the start of steering, the rear wheels are momentarily shifted to the opposite phase, and the steering angle of the front wheels is increased to balance the yaw rate and the lateral acceleration. Thereby, the rising of the rotational motion of the vehicle is improved. Then, the next moment, returning to steady four-wheel in-phase steering,
It is possible to turn around the target trajectory while keeping the sideslip angle at zero.

In order to realize such a front-wheel phase advance control, a variable steering gear ratio device that can vary the vehicle steering angle with respect to the steering wheel steering angle is employed.

Conventionally, devices capable of varying the steering gear ratio include those disclosed in JP-A-48-31636, JP-A-53-107036, JP-A-62-26162, JP-B-54-34212, and JP-B-56.
-45824 and the like.

In each of these devices, one or two sets of planetary gear mechanisms are provided between an input shaft connected to a steering wheel and an output shaft connected to a steering gear. A worm is provided on the ring gear of the one set of planetary gear mechanisms or the second set of planetary gear mechanisms, and the worm is meshed with a worm gear directly connected to the motor. When the steering wheel is operated, the rotation is transmitted to the output shaft via the planetary gear mechanism, and when the ring gear is rotated by operating the motor from that state, the gear ratio is changed by the rotational displacement of the ring gear. It has become.

(Problems to be Solved by the Invention) By the way, a ring gear displacement mechanism combining a motor-driven worm gear and a worm can prevent a ring gear from being inadvertently moved by using a self-locking function of the worm gear. Since the gear ratio cannot be obtained unless the ring gear is accurately rotated to a predetermined displacement by the above rotation, the control becomes considerably complicated. In addition, since the electric control is performed, there is a problem that the reliability against noise, radio interference, and the like is poor.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a variable steering gear ratio device capable of performing phase advance control with simple and highly reliable control. It is in.

(Means for Solving the Problems) In order to achieve the above object, a variable steering gear ratio device of the present invention slides a ring gear displacement mechanism for displacing a ring gear in a rotation direction into a valve body and into the valve body. A freely provided spool, a sleeve slidably provided on the outer periphery of the spool, a fluid inlet port and a fluid outlet port for steering reaction force provided on the valve body, and the spool provided on an end face side of the sleeve. A pair of pressure receiving chambers facing the sleeve end, and flow control between the fluid inlet port and the fluid outlet port and each of the pressure receiving chambers provided on the spool and the sleeve in accordance with the relative displacement of the spool and the sleeve. An opening / closing passage for positioning the sleeve with respect to the spool, and transmitting a displacement of the sleeve provided in the valve body to a ring gear of the planetary gear mechanism. And a pair of control pressure ports provided on the valve body for inputting control pressure for ring gear displacement to the spool end.

(Operation) According to the variable steering gear ratio device of the present invention, the relative position between the two is maintained such that the sleeve becomes zero with respect to the spool by the fluid flow control in the steady state. With this follow-up performance, a steering reaction force that constantly sets the ring gear of the planetary gear mechanism at a predetermined position is output.

When a control pressure with a variable gear ratio is applied from one of the control pressure ports, the spool is displaced in the axial direction according to the control pressure.
Then, the sleeve is displaced following the displaced spool so that the relative position maintains the zero relationship, and the ring gear of the planetary gear mechanism is displaced via the transmission member. Accordingly, the front wheels can be phase-advanced by simple control using a fluid pressure free from obstacles such as noise.

(Embodiment) Hereinafter, the present invention will be described with reference to an embodiment shown in FIGS. 1 to 7. FIG. 5 shows a four-wheel steering system for a vehicle to which the present invention is applied, wherein 1a and 1b are left and right front wheels. The front wheels 1a and 1b are rotatably supported by knuckles 2a and 2b which are supported so as to be swingable in a horizontal direction with respect to a vehicle body (not shown). Knuckles 2a, 2b are tie rods 3a,
For example, it is connected via a 3b to a vehicle speed-sensitive power steering 6 formed by combining a rack 4 and a pinion 5. That is, the power steering 6 includes a steering gear assembly 9 having a rack 4, a pinion 5, a rotary valve 7, and a torsion bar 8, and a power cylinder device 10 for steering connected to the rotary valve 7.
(Piston 12 connected to rack 4 in power cylinder 11
And an engine-driven oil pump 13 (for power steering) that supplies hydraulic pressure to the rotary valve 7. And the power cylinder device 10
The piston rods 12a, 12b on both sides of the piston 12 are connected to the tie rods 3a, 3b.

A valve input shaft 7a of a rotary valve 7 connected to the pinion 5 and an torsion bar 8, which are input portions of a steering gear assembly 9, are provided with a variable steering gear ratio device 14, an intermediate joint 15, a column shaft A steering wheel 17 is connected via a link 16. Thus, when the steering wheel 17 is operated, the rack 4 is driven in the same direction as the steering wheel 17. At the same time, the hydraulic pressure generated by the oil pump 13 is supplied to the left chamber 18 and the right chamber 19 formed on both sides of the piston 12 through the rotary valve 7 so that the steering force of the steering wheel 17 can be assisted. The oil pump 13 is a pump whose discharge flow rate decreases as the rotation speed of the engine 20 increases from a certain region.

Here, the variable steering gear ratio device 14 will be described. The variable steering gear ratio device 14 is provided with two sets of planetary gear mechanisms 21 and 22 on the steering gear assembly 9 as shown in detail in FIGS. And a control valve 23 (corresponding to a ring gear displacement mechanism).

In detail, 37 is a case installed on the upper end of the case 9a of the steering gear assembly 9, and 37a is the case 3
7 is a screw-type cap for closing the upper opening. The case 37 and the cap 37a are fixed to the case 9a by bolts 35 penetrating therethrough and nuts 36 screwed to bolt ends, and constitute a body of the variable steering gear ratio device 14. An input shaft 24 (corresponding to an input shaft) is rotatably provided coaxially with the valve input shaft 7a (corresponding to an output shaft) on the upper side in the case 37. 24a is a bearing that rotatably supports the input shaft 24.
A sun gear 25 is provided integrally with a lower outer periphery of the input shaft 24. Around this sun gear 25, a ring gear 26 supported on the case 37 side is provided. Further, between the ring gear 26 and the sun gear 25, four sets of planetary gears 27 meshing with both gears are provided, and constitute the first stage planetary gear mechanism 21. This cap 37a
The intermediate joint 15 is connected to an upper part of the input shaft 24 protruding from the upper part.

The end of the valve input shaft 7a protrudes upward from the upper end opening of the case 9a. And this case
A sun gear 28 having the same specifications as the first-stage planetary gear 21 is integrally provided on the outer periphery of the end of the valve input shaft 7a that enters the inside 37. A ring gear 29 having the same specifications as the first stage is provided in a case 37 around the sun gear 28. The first stage planetary gear 27 is provided between the ring gear 29 and the sun gear 28 via a shaft 30.
There are provided four rotatable planetary gears 31 which are coaxial with the planetary gear mechanism 22 and constitute a second stage planetary gear mechanism 22. In addition, the planetary gear 27 and the planetary gear 31
A holder 32 for holding 30 and a holder 33 for regulating the gear provided at the end of the shaft are supported so as to be movable in the circumferential direction around the axis of the valve input shaft 7a.

An adjuster 38 for regulating the vertical movement of the bearing 24a is provided on the cap 37a, and the planetary gear mechanisms 21 and 22 are provided.
Are assembled to the steering gear assembly 9 in a predetermined manner. Numeral 39 is a seal member, numeral 40 is a nut for preventing the adjuster 38 from loosening, and numeral 41 is a spacer for restricting the vertical movement of the ring gears 26, 29.

The distal end of the valve input shaft 7a is inserted into a concave portion 43 provided at the shaft end of the input shaft 24. The end of the torsion bar 8 is connected to the insertion end of the valve input shaft 7a by a pin 44, and the steering wheel 1 is fixed with the ring gears 26 and 29 fixed.
When the steering wheel 7 is steered, the steering angle of the steering wheel 17 can be transmitted to the rotary valve 7 and the torsion bar 8 at the same ratio through the first and second stage planetary gear mechanisms 21 and 22. However, between the insertion end of the valve input shaft 7a and the concave portion 43, a metal bush 45 for preventing rattling in the circumferential direction is interposed.

Further, the first-stage planetary gear mechanism 21 is provided with a safety device 46 for preventing excessive torque from being applied from the steering wheel 17. Specifically, the safety device 46 has a concave portion 47 on the outer peripheral surface of the ring gear 26. Also, on the case 37 side, a pin part 48 and a pin part 4
There is provided a set screw composed of a spring 49 and an adapter component 50 for urging the connector 8 in the fitting direction. And
With this structure, the rotation of the ring gear 26 in the rotational direction is restricted by the concave and convex fitting, and when an excessive steering force exceeding the preload from the steering wheel 17 enters the ring gear 29, the concave and convex fitting is released and the ring gear 26 is released. Can be rotated to protect the planetary gear mechanisms 21 and 22 from excessive torque. As shown in FIG. 4, the input shaft end and the valve input shaft end in the fitted state are loosely fitted between the pair of fan-shaped projecting portions 7b, 7b. A stopper 14a is provided in combination with a pair of projecting pieces 24a, 24a, and when the ring gear 26 rotates a certain amount, both the projecting piece 7b and the projecting piece 24a come into contact with each other. Thus, the steering force from the steering wheel 17 is directly transmitted from the input shaft 24 to the valve input shaft 7a.

The control valve 23 is mounted on a case 37 on which the planetary gear mechanisms 21 and 22 are mounted.

In other words, regarding the control valve 23, reference numeral 51 denotes an elongated valve body integrally provided in a case portion adjacent to the ring gear 29 along a direction perpendicular to the center of the planetary gear mechanism 22. In the valve body 51, the ring gear 29
A substantially cylindrical valve chamber 52 is formed along a direction perpendicular to the axis of the valve chamber 52. A spool 53 is provided in the valve chamber 52. One end of the spool 53 is slidably supported by a plug 54 attached to an end of the valve chamber 52, and the other end is slidably supported by a plug 56 attached to the other end of the valve chamber 52 via an adapter 55. Supported. The end faces of the shafts of the spool 53 face the holes 54a and 56a (corresponding to the control pressure ports) of the plugs 54 and 56. A spring chamber 55a is formed inside the adapter 55. And, in this spring chamber 55a,
A spring 58 spanned between a washer 56a slidably fitted to the small diameter portion 53a on the outer periphery of the end of the spool 53 and a snap ring 57 fixed to the end of the small diameter portion 53a is housed,
The spring 53 positions the spool 53. Reference numeral 59 denotes a nut for preventing the plugs 54 and 56 and the adapter 56 from loosening.

A plate-shaped lever 60 (corresponding to a transmission member) is provided on the outer periphery of the spool 53 so as to movably penetrate the shaft of the spool 53. The lever 60 is arranged on a line that intersects the axis of the ring gear 29 at right angles. And lever 60
The arc portion formed at the end on the side of the ring gear 29 is engaged with a groove 62 formed on the outer peripheral surface of the ring gear 29 through a through hole 61 formed in the valve body portion and the case portion. An arc formed at the remaining narrow end of the lever 60 is an adapter attached to the valve chamber 52 so as to cover the end.
The lever is rotatably engaged with a groove 65 of a plate 64 provided on the inner bottom surface of the spool 63 so that the entire lever can be rotated along the axis of the spool 53 with the end on the plate 64 side as a fulcrum. 66 is a locking nut of the adapter 63, and 67 is a corrugated washer interposed between the plate 64 and the inner bottom surface of the adapter 63.

A collar 68 is slidably fitted on the outer periphery of the spool portion on the plug 54 side, and a sleeve 69 is slidably fitted on the outer periphery of the spool portion on the plug 56 side with the lever 60 interposed therebetween. The collar 68 and the sleeve 69 are provided with a spring 7 provided between the outer end thereof and the plug 54 and the adapter 55.
By the elastic force (preload) of 0a and 70b, the lever 60 is pressed on both sides of the lever 60, and the three parts including the lever 60 are positioned on the spool 53. On the outer peripheral surface of the spool 53 covered with the sleeve 69, two inflow-side chambers 71, 72 each formed of an annular groove are provided in parallel. On the other hand, chambers 71, 7
Two outflow-side chambers 73 to 75 (each of which corresponds to an opening / closing passage) constituted by a groove are provided at the boundary portion of No. 2. The chamber 71 is provided with a passage provided inside the spool 53.
Via a 76 (corresponding to an opening / closing passage), it communicates with a pressure receiving chamber 77 which also serves as a spring chamber formed between the collar 68 and the plug 54. Further, the chamber 72 communicates with a pressure receiving chamber 79 which is formed between the sleeve 69 and the adapter 55 and also serves as a spring chamber, via a passage 78 (corresponding to an opening / closing passage) similarly provided inside the spool 53. I have. The center chamber 74 on the outflow side is connected to the discharge section of the oil pump 13 via a port 80 (corresponding to a fluid inlet port) provided in the valve body 51. The remaining chambers 73 and 75 are connected to an inlet port (not shown) of the rotary valve 7 of the steering gear assembly 9 via a port 81 (corresponding to a fluid outlet port) provided in the valve body 51, and the oil pump 13 A follow-up type servo valve (spool valve) that can hold the ring gear 29 at a predetermined position by using the generated hydraulic pressure or increase and increase the input steering angle is configured. That is, since the oil of the oil pump 13 flows into the pressure receiving chambers 77, 79 facing the sleeve ends through the passages 76, 78, the second-stage ring gear 29 is rotationally displaced by steering, and the sleeve 69 moves in the axial direction. When displaced, opening and closing the chambers 71 and 72 and the chambers 73 to 75 opens the displaced passage on the pressure receiving chamber side and supplies hydraulic pressure to the pressure receiving chamber. The returned sleeve 69 is returned to the original position. The return output is used as a steering reaction force to always return the ring gear 29 to the original position (localization). When a control pressure for displacing the spool 53 is applied from the plug 54 and the plug 56, the sleeve 69 moves following the displacement of the spool 53 and rotates the lever 60. And this lever 60
, The ring gear 29 is rotated to the further increased side (variable steering gear ratio).

On the other hand, 82a and 82b are left and right rear wheels. The rear wheels 82a, 82b
It is supported by a double wishbone type rear wheel suspension with a toe control mechanism. That is, the rear wheel suspension is
A pair of upper and lower lateral arms composed of 84 and a lower arm 85 are provided, and an arm formed by connecting a toe control arm 86 and a trailing arm 87 by an intermediate joint 88 is connected. The rear wheels 82a and 82b are supported on the arm ends via wheel supports (not shown). The intermediate joint 88 includes a pivot shaft 89 such as a pin whose rotation axis is set substantially in the vertical direction, and has a structure capable of steering the rear wheels 82a and 82b according to the displacement of the intermediate joint point.

Further, a double rear power cylinder 90 is provided on the cross member 83 so as to connect the left and right pivot shafts 89, 89 of the rear wheel suspension. That is, the rear power cylinder 90 includes a cylinder 9 having a large-diameter cylinder chamber 91 formed in the center and a pair of small-diameter cylinder chambers 92a and 92b formed on both sides.
4, a piston part 95a having a diameter corresponding to the cylinder chamber 91 is provided at the center.
And a piston 95 having a piston portion 95b on both sides having a diameter corresponding to the cylinder chambers 92a and 92b is slidably provided.
In addition, piston rods 96a, 96
It is constructed by connecting b. A left chamber 97a and a right chamber 97b that receive an output for the same phase are formed in a portion where the cross-sectional area of the cylinder chamber 91 partitioned by the piston portion 95a is large. Room 97
The cross-sectional areas of the cylinder chambers 92a and 92b arranged side by side with a and 97b receive the output for phase in a small space. This cylinder
94 is fixed to the cross member 83 with the axial direction defined in the left-right direction. The left piston rod 96a is connected to the pivot shaft 39 of the left intermediate joint 38, and the right piston rod 96b is connected to the pivot shaft 39 of the right intermediate joint 38. 82a and 82b can be steered.

The left chamber 97a and the right chamber 97 of the rear power cylinder 90
b is connected to an in-phase control valve 98 via an oil passage 99, and the cylinder chambers 92a, 92b of the rear power cylinder 90
Are connected to the phase control valve 100 via oil flow paths 101a and 101b.

As the control valve 98 for the same phase, a spool valve as shown in FIG. 6 is used. Specifically, the spool valve has a spool 221 whose both ends are urged by a pair of springs 220 in a cylindrical case 102. Two annular grooves 222 and 223 are provided side by side on the outer periphery of the spool 221. On both sides of the peripheral wall of the case 102 facing the spaces of the grooves 222 and 223, reserve ports 224a and 224b and pump-side ports 225a and 225b are respectively provided symmetrically around the convex portion between the grooves, and further faces the space of the grooves 222 and 223. Actuator-side ports 226 and 227 are provided at the center of the peripheral wall of the case 102, respectively. Pilot ports 228 and 229 for applying control pressure to the spool end are provided at both ends of the case 102. The actuator side ports 226 and 227 are
Connected to 9.

The left and right chambers 18 and 19 of the power steering 6 are connected to the pilot ports 228 and 229 of the in-phase control valve 98 via the oil passage 103, respectively. When a power stay pressure is generated, the neutral spool 221 is displaced. Then, switching between the reserve ports 224a, 224b and the pump ports 225a, 225b is performed. The pump ports 225a and 225b of the control valve 100 are connected to an oil pump 105 that is driven by a differential gear 104 and generates a hydraulic pressure according to the vehicle speed (high vehicle speed: increased hydraulic pressure). Thus, the hydraulic pressure according to the vehicle speed and the amount of movement of the spool 221 can be supplied to the left chamber 97a or the right side 97b in the steering direction of the rear power cylinder 90. The reserve ports 224a and 224b are connected to the reserve tank 106 receiving the return of the power steering 6.

As the phase control valve 100, a four-port throttle switching valve of a spool valve type is used. FIG. 7 shows a schematic structure of the switching valve.

Describing the switching valve, 107 is a cylindrical case having ports 108 and 109 for pilot pressure on both sides, and 110 is a spool provided in this case 107. Then, both ends of the spool 110 are formed with bearings 111 formed on the inner surface of the case.
, So that the entire spool can slide along the axial direction of the case 107. A pair of springs 112 and 113 are interposed between the spool end and the case end to position the spool 110.
The spring chambers outside the bearings that accommodate the springs 112 and 113 communicate with the ports 108 and 109, respectively. These ports 108 and 109 are connected to the middle part of the oil flow passage 103 via the branch passage 132 so as to apply a power steering pressure as a control pressure to the spool end.

Further, the bore of the case 107 sandwiched between the bearings 111 has a large diameter. In the center of the spool portion exposed to the large space portion, an outer diameter sleeve 11 corresponding to the lumen portion is provided.
4 is provided slidably. Both ends of the sleeve 114 are connected to a pair of springs 115, 116 fixed to the spool 110.
Energized by the entire sleeve
Positioned above. In each space formed at the end of the sleeve, pressure receiving chambers 117 and 118 serving as spring chambers are formed.

On the outer peripheral surface of the spool 110 covered by the sleeve 114, two chambers 119 and 120 each formed by an annular groove are provided in parallel. On the inner peripheral surface of the sleeve 114, there are three chambers 121 to 1 which are located at the boundary between the chambers 119 and 120 and are formed of annular grooves.
23 are provided. The chambers 119 and 120 are communicated with actuator ports 126 and 127 formed in the outer periphery of the case through sleeves 114 and passage spaces 124 and 125 formed in the inner peripheral surface of the case, respectively. And port 12
6,127 are connected to oil flow paths 101a, 101b. Room 122 also
It communicates with an oil supply port 129 provided in the case 107 via a passage space 128. The port 129 is connected to the engine 2 together with the oil pump 13 via an oil supply passage 130.
It is connected to the discharge part of a constant flow type (constant discharge flow rate) oil pump 131 driven by zero.

The remaining chambers 121 and 123 communicate with reservoir ports 135 and 136 formed in the outer periphery of the case through sleeves 114 and passage spaces 133 and 134 formed in the inner peripheral surface of the case, respectively. These ports 135 and 136 are connected in parallel by an oil passage 137, and are connected to the reservoir tank 106. In this parallel oil passage 137, through communication passages 138 and 139,
The pressure receiving chambers 117 and 118 on both sides of the sleeve are connected in parallel, so that oil from the oil pump 131 can flow into the pressure receiving chambers 117 and 118. Also, in each communication passage 138, 139,
Each is provided with a check valve 140 for regulating the flow to the reservoir tank 106 side. Further, a variable orifice 141 (or a variable choke) is interposed between a communication path between the check valve 140 and the reservoir port 135 and a communication path between the check valve 140 and the reservoir port 136. A communication path 142 for generating a differential pressure is connected to the communication path 142. The variable orifice 141 is connected via a flow path 144 to a vehicle speed sensitive pressure generator 143 built in the differential drive oil pump 105, and the variable speed orifice 141 is connected to the vehicle speed sensitive pressure generator 143.
Thus, the throttle amount of the variable orifice 141 can be changed in response to the vehicle speed by the pilot pressure generated from the throttle valve.

As a result, the control valve 100 determines the rate of change of the pilot pressure of the power steering 6 by cutting the steering wheel 17 from the displacement of the spool 110 due to the pilot pressure applied to the spool end and the relative displacement of the sleeve 114 with respect to the spool 110. A phase hydraulic pressure can be generated according to the vehicle speed (high vehicle speed: reduced hydraulic pressure). That is, at the start of the steering operation, the control valve 100 can supply an output for steering the rear wheels 82a, 82b in a direction opposite to the front wheels 1a, 1b to the cylinder chamber 92a or the cylinder chamber 92b of the rear power cylinder 90. I have.

The oil flow paths 101a, 101b connected to the phase control valve 100 are connected to the plugs 54, 56 of the phase advance mechanism 14 via branch paths 145, 145, and the rear wheels 82a, 82b
At the same time as the phase, the front wheels 1a and 1b can be advanced to the side to be increased.

Next, the operation of the four-wheel steering device configured as described above will be described.

When the vehicle is traveling straight, the steering wheel 17 is in a neutral state, so that the front wheels 1a, 1b and the rear wheels 82a, 82b are oriented in the straight traveling direction.

When the steering wheel 17 is turned, for example, to the right turning side (at a middle or high speed) in order to turn from such a straight traveling state (turn-in), the rate of change of the power steering pressure and the vehicle speed with respect to the turned steering angle. Accordingly, the rear wheels 82a and 82b momentarily have opposite phases, and the front wheels 1a and 1b momentarily increase the steering angle from the input steering angle.

Specifically, when the steering wheel 17 is operated, this rotation is transmitted to the sun gear 25 of the first-stage planetary gear mechanism 21 via the column shaft 16, the intermediate joint 15, and the input shaft 24. Here, the ring gear 26 receives operating force, but the ring gear 26 is
Since the rotation is fixed to 37, the rotation is further transmitted to the planetary gear 31 of the second-stage planetary gear mechanism 22 via the planetary gear 27. In addition, the ring gear 29 of the second-stage planetary gear mechanism 22 tries to rotate by receiving the steering force of the ring gear 29, but the ring gear 29 always has a force (oil oil) generated by the control valve 23 to return the ring gear 29 to the original position. pump
With the hydraulic pressure generated at 13, the force that always tries to make the relative displacement of the sleeve 69 relative to the spool 53 zero) acts as a steering reaction force, so the rotation of the planetary gear 31
From 28, it is transmitted to the valve input shaft 7a and the torsion bar 8. That is, when the ring gear 29 rotates by receiving the steering force, the lever 60
Rotationally displaces in the same direction as the ring gear 29 with 65 as a fulcrum. At this time, the sleeve 69 is also moved by the movement of the lever 60. That is, a relative error occurs between the sleeve 69 and the spool 53. Then, a hydraulic pressure is generated in the control valve 23 due to the relative displacement. This hydraulic pressure generates a force that returns the sleeve 69, the lever 60, and the ring gear 29 to their original positions, that is, a position where the relative displacement with respect to the spool 53 is zero, and this force acts as a steering reaction force.
Specifically, when the ring gear 29 receives the steering force and tries to turn counterclockwise, the lever 60 rotates in the same direction about the groove 65 as a fulcrum. This allows the sleeve 69 to be plugged
Sliding in the direction of the 54 side, relative displacement occurs with the spool 53. Then, the flow rate from the oil pump 13 flows into the chamber 71, and hydraulic pressure is generated in the chamber 71 by the throttle effect of the chamber 71. Then, this hydraulic pressure flows into the pressure receiving chamber 77 through the passage 76, and moves the sleeve 69 to the right. This acts as a holding force in the original position.

Then, the rotation transmitted to the torsion bar 8 is transmitted to the pinion 5, and the front wheels 1a and 1b are
Steering in the direction of turning. At the same time, the rotary valve 7 is operated by the rotation transmitted to the valve input shaft 7a, and the hydraulic pressure generated by the oil pump 13 is supplied to the right chamber 19 of the power cylinder 11 to assist the steering of the steering wheel 17.

On the other hand, the spool of the in-phase control valve 98 is stroked in accordance with the power stay pressure of the power steering 6. Then, the oil discharged from the oil pump 105 is controlled by the stroke of the spool. That is, the control valve 98 generates a hydraulic pressure according to the vehicle speed (rear wheel rotation speed) and the power stay pressure, that is, the steering state of the front wheels 1a and 1b. Then, this hydraulic pressure flows into the left chamber 97a of the rear power cylinder 90 that is steered to the same phase side.

On the other hand, when the power stay pressure is applied as pilot pressure from the pilot pressure port 109, the phase control valve 100 controls the spool 11 by an amount proportional to this pressure.
0 is displaced to the left (x ₁ ).

The amount of displacement is related to the product of the area of the end face of the spool 110 and the pilot pressure, and the elastic force of the springs 112 and 113.

_{a 1 · F 1 = K 1} · x 1 + f 1 i.e., is represented by _{x 1 = a 1 · F 1} -f 1 / K 1. However, a ₁ is the area of the spool end faces, K ₁ is the spring constant of the spring 115 and 116, f ₁ preload value of the spring, F ₁ is the pilot pressure.

At this time, the displacement of the spool 110 causes the sleeve 114
Also try to move in the same direction. This requires that the oil in the pressure receiving chamber 117 move to the pressure receiving chamber 118 through the communication passage 142. However, since the variable orifice 141 is incorporated in the communication passage 142, the differential pressure ΔP
Occurs. Here, ΔP is represented as follows.

^{ΔP · δ · Qb 2/2} · Cd · d 2 where, [delta] is the fluid density, Qb is the flow rate through the throttle section, the cross-sectional area of d the diaphragm portion, Cd is a flow coefficient.

In the case of a choke structure, ΔP = 8 · π · μ · l / d ² . Here, 1 is the length of the throttle portion, and μ is the viscosity coefficient of the oil.

Then, due to this differential pressure ΔP, the sleeve 114 is shifted relative to the spool 110 to the right. The relative displacement y at this time is represented by y = ΔP · b ₂ −f ₂ / K ₂ . However, b ₂ is the area of the end face of the sleeve, K ₂ is the spring constant of the spring 112 and 113, f ₂ is the pre-load value of the spring.

Since a constant flow of oil generated by the oil pump 131 is supplied from the oil supply port 129, a differential pressure proportional to the relative displacement y is generated from the actuator ports 126 and 127. That is, the relative displacement y is, WaiarufaderutaPiarufakyubiarufaeruarufa1 / is a function of _{^{d 2, Qb = b 2 ·}} (x 1 -y) / t where, t is time holds (x ₁ -y ) ∝Pilot pressure.

From the ports 126 and 127 for the actuator,
The output oil pressure decreases according to the vehicle speed, and the oil pressure (differential pressure) controlled according to the rate of change of the power steering pressure is output.

The hydraulic pressure (differential pressure) is applied to the rear power cylinder 90
The cylinder chamber 92b is supplied with an output for phasing the rear wheels 82a and 82b, and is supplied to the plug 54 of the variable steering gear ratio device 14.
Is supplied as an output that increases the steering angle of the front wheels 1a and 1b.

Then, the output of the cylinder chamber 92b that tries to steer the rear wheels 82a, 82b in the opposite direction to the front wheel, and the output of the left chamber 97a that tries to steer the rear wheels 82a, 82b in the same direction as the rear wheels. The rear wheels 82a and 82b are steered according to the steering angle on the opposite phase obtained by the synthesis.

In the variable steering gear ratio device 14, when a control pressure is applied to the plug 54, the spool 53 slides rightward in proportion to the hydraulic pressure. Then, the spool 53 and the sleeve
Relative displacement occurs between 69 and the flow rate from oil pump 13
It flows into 71. As a result, hydraulic pressure is generated by the throttle effect of the chamber 71, and the hydraulic pressure is transmitted through the passage 76 to the pressure receiving chamber.
It is led to 77. Therefore, sleeve 69, collar 68
Follows the spool 53 and moves to a position where the relative position with respect to the spool 53 becomes zero. And this sleeve 6
9, the movement of the collar 68 causes the lever 60 to pivot about the plate 64 side. Thus, the ring gear 29 is rotated clockwise.

Here, since the planetary gears 27, 31 are fixed by the steering wheel 17 held by the driver, the rotation of the ring gear 29 is transmitted to the valve input shaft 7a and the torsion bar 8, and the valve input shaft 7
a, The torsion bar 8 is turned clockwise (advance control).

However, the front wheel steering angle can be controlled by a composite value of the two inputs, that is, the input by the driving vehicle from the steering wheel 17 and the input by the hydraulic pressure from the plugs 54 and 66.

Therefore, apply control pressure to plugs 54, 56 and
By applying pressure from 80, variable control of the steering gear ratio can be performed while appropriately generating steering reaction force, and control is easier than electronic control. That is, the phase advance control can be performed by simple control. In addition, since the gear ratio is changed using the fluid pressure, reliability against noise, radio interference, and the like is high.

In addition, since the set screw and the stopper portion 14a prevent the planetary gear mechanisms 21 and 22 from receiving more input than necessary, the planetary gear mechanisms 21 and 22 can be reduced in size and weight accordingly. That is, when the steering wheel 17 is further strongly steered at the full steering angle of the steering wheel 17, the fitting between the pin component 50 and the concave portion 47 is released due to the displacement of the spring 49 in the compression direction. Subsequently, the projecting pieces 24a, 24a at the end of the input shaft come into contact with the projecting pieces 7a, 7a of the valve input shaft 7a,
The steering force from the steering wheel 17 is transmitted directly to the valve input shaft 7a. This eliminates the need for the planetary gear mechanisms 21 and 22 to endure an excessive steering force, thereby reducing the size and weight of the parts of the planetary gear mechanisms 21 and 22.

However, when the rate of change of the power steering pressure disappears, only the output from the in-phase control valve 98 according to the vehicle speed is entered, and the vehicle enters the original steady-state four-wheel in-phase steering (normal in-phase four WS).

In the embodiment, the rate of change of the power steering pressure of the front wheels 1a, 1b is used as the control pressure, but a pressure output means constituted by a hydraulic circuit using the steering angular velocity as the control pressure may be used. Also in this case, a control pressure including a vehicle speed factor may be used.

Further, in one embodiment, the present invention is applied to a variable steering gear ratio device using two sets of planetary gear mechanisms, but may be applied to a variable steering gear ratio device having one set of planetary gear mechanisms.

(Effects of the Invention) As described above, according to the present invention, a simple control of applying a control pressure from a control pressure port and applying a pressure from a fluid inlet port, while appropriately generating a steering reaction force,
The steering gear ratio can be varied, and the control is simpler than the electronic control.

In addition, since the gear ratio is changed using the fluid pressure, reliability against noise, radio interference, and the like is high.

[Brief description of the drawings]

1 to 7 show an embodiment of the present invention.
FIG. 2 is a partially sectional perspective view showing the variable steering gear ratio device of the present invention, FIG. 2 is a sectional view showing the vicinity of two sets of planetary gear mechanisms, FIG. 3 is a sectional view showing the structure of a ring gear displacement mechanism, FIG. 4 is a sectional view taken along the line AA in FIG. 2, FIG. 5 is a configuration diagram showing a four-wheel steering system to which a steering gear ratio variable device is applied, and FIG. 6 shows a control valve for the same phase. FIG. 7 is a sectional view showing a phase control valve. 7a …… Valve input shaft (output shaft), 14
…… Steering gear ratio variable device, 21,22 …… Planetary gear mechanism, 23 …… Control valve (ring gear displacement mechanism), 24 …… Input shaft (input shaft), 54
a, 56a: plug hole (control pressure port), 60: lever transmission member, 71 to 76, 78 ... chamber, passage (opening / closing passage), 7
7,79… Pressure receiving chamber, 80 …… Port (fluid inlet port), 81
... port (fluid outlet port).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadao Tanaka 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Keiji Fujii 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Masayoshi Nishimori 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Hiroyuki Masuda 1 Nakashinagiri, Hashime-cho, Okazaki City, Aichi Prefecture Address: Mitsubishi Motors Engineering Co., Ltd. Okazaki Plant (56) References JP-A-62-26162 (JP, A) JP-A-63-143472 (JP, U)

Claims (1)

(57) [Claims] 1. A variable steering gear ratio device comprising: a planetary gear mechanism provided between an input shaft and an output shaft; and a planetary gear mechanism provided with a ring gear displacement mechanism for displacing the ring gear in a rotational direction. The mechanism includes a valve body, a spool slidably provided in the valve body, a sleeve slidably provided on the outer periphery of the spool, a steering reaction force fluid inlet port and a fluid outlet provided in the valve body. A port, a pair of pressure receiving chambers provided on the end face side of the sleeve and facing the sleeve end, and the fluid inlet port and the fluid outlet port provided on the spool and the sleeve in accordance with the relative displacement of the spool and the sleeve. An opening / closing passage for controlling the flow between the pressure receiving chambers and positioning the sleeve with respect to the spool; A transmission member for transmitting the sleeve displacement to the ring gear of the planetary gear mechanism, and a pair of control pressure ports provided on the valve body for inputting a control pressure for ring gear displacement to the spool end. Variable steering gear ratio device.